A comparative analysis of growth traits in Triploid and Diploid Genotypes of the South African abalone, Haliotis midae

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Brink, D.

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Prins, Nico

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Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.

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2011-11-23T13:21:15Z

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2011-12-05T13:26:49Z

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2011-11-23T13:21:15Z

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2011-12-05T13:26:49Z

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2011-12

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http://hdl.handle.net/10019.1/18082

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Thesis (MScAgric)--Stellenbosch University, 2011.

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ENGLISH ABSTRACT: Abalone production is the largest financial contributor to aquaculture in South Africa and
practically all of the abalone produced is exported to Asia. This means that the product
must be globally competitive and many technologies have been applied to this cause.
One that specifically shows great promise for bivalve mollusc production is triploidy; more
precisely, sterility due to the induction of aneuploidy.
Under normal maturation, energy is diverted from somatic growth through sexual
maturation, therefore inhibiting or retarding gametogenesis through a process such as
aneuploidy is expected to increase growth and decrease the time to marketing.
Two studies preceding this one investigated the induction of triploidy through hydrostatic
shock (De Beer, 2004) and the comparative growth rate of triploid genotypes from 8 to 24
months, prior to the onset of sexual maturation (Schoonbee, 2008). During this
comparative growth stage, no convincing statistical evidence of faster growth or of
seasonal environmental effects could be obtained.
It was recommended that growth between triploid and diploid variants be compared
during the age period when sexual maturity becomes a factor to determine whether
triploidy in Haliotis midae is a useful biotechnological tool to improve biological
productivity and global competiveness of the abalone industry.
The growth measured as shell length and wet weight in the period from 29 to 62 months
showed a statistically significant difference in mean weight and mean length with diploids
showing a superior growth rate compared to their triploid siblings. This difference of 1.99
mm and 5.13 g was however not perceived as being commercially significant.
Important production parameters including canning yield percentage and gonadosomatic
index were also measured during this trial. For both these parameters, the triploid
genotype showed statistically and commercially significant improvement of 10.68%
increased canning yield and 28.42% reduction in gonadosomatic index when compared
to their diploid counterparts.
Triploid abalone was found to be not completely sterile; gametes and even mature
gonads were observed in some instances. Even though complete sterility was not
achieved there appeared to be a retarded gonadosomatic development in triploid variants. The delay in sexual maturation, together with the improvement in canning yield,
may justify triploidy’s commercial application, despite its reduced growth rate.